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Abstract:

A power generating apparatus includes a rotating shaft, a hydraulic pump
driven by the rotating shaft, a hydraulic motor driven by pressurized oil
supplied from the hydraulic pump, and a generator coupled to the
hydraulic motor. Each of the hydraulic pump and motor includes working
chambers each defined by a cylinder and a piston, a high pressure
manifold and a low pressure manifold. Each of the high and low pressure
manifolds includes branch channels connected to the working chambers and
a merging channel connected to a high or low pressure oil line. The
branch channels are equipped with high or low pressures valves, joined
together and merged into the merging channel.

Claims:

1. A power generating apparatus of renewable energy type which generates
power from a renewable energy source, comprising: a rotating shaft driven
by the renewable energy source; a hydraulic pump driven by the rotating
shaft; a hydraulic motor which is driven by pressurized oil supplied from
the hydraulic pump; a generator coupled to the hydraulic motor; a high
pressure oil line through which a discharge side of the hydraulic pump is
in fluid communication with an intake side of the hydraulic motor; and a
low pressure oil line through which an intake side of the hydraulic pump
is in fluid communication with a discharge side of the hydraulic motor,
wherein each of the hydraulic pump and the hydraulic motor comprises: a
plurality of working chambers each of which is surrounded by a cylinder
and a piston reciprocating within the cylinder; a high pressure manifold
including first branch channels each connected to the working chambers
and a first merging channel connected to the high pressure oil line, the
first branch channels joining together and merging into the first merging
channel; a low pressure manifold including second branch channels each
connected to the working chambers and a second merging channel connected
to the low pressure oil line, the second branch channels joining together
and merging into the second merging channel; a plurality of high pressure
valves which are respectively provided in the first branch channels of
the high pressure manifold to open and close the first branch channels; a
plurality of low pressure valves which are respectively provided in the
second branch channels of the low pressure manifold to open and close the
second branch channels; and a casing which accommodates the working
chambers, the high pressure manifold, the low pressure manifold, the high
pressure valves and low pressure valves.

2. The power generating apparatus of renewable energy type according to
claim 1, wherein at least one of the hydraulic pump and the hydraulic
motor comprises a cylinder block accommodated in the casing, the
cylinders being provided inside the cylinder block, and wherein the first
branch channels and the second branch channels of the at least one of the
hydraulic pump and the hydraulic motor are arranged inside the cylinder
block.

3. The power generating apparatus of renewable energy type according to
claim 1, wherein the first merging channel of the high pressure manifold
of at least one of the hydraulic pump and the hydraulic motor is provided
inside an endplate that forms an end face in a direction of a rotation
central axis of the at least one of the hydraulic pump and the hydraulic
motor.

4. The power generating apparatus of renewable energy type according to
claim 2, wherein a plurality of cylinder arrays are arranged inside the
cylinder block in a circumferential direction of the at least one of the
hydraulic pump and the hydraulic motor, each of the cylinder arrays being
constituted of the cylinders aligned in a direction of a rotation central
axis of the at least one of the hydraulic pump and the hydraulic motor,
wherein a high pressure communication channel is provided inside the
cylinder block between adjacent two of the cylinder arrays, and wherein
the first branch channels connected to the working chambers of the
cylinders belonging to one or the adjacent two of the cylinder arrays are
in fluid communication with the first merging channel via the high
pressure communication channel.

5. The power generating apparatus of renewable energy type according to
claim 2, wherein in the at least one of the hydraulic pump and the
hydraulic motor, an annular space between the casing and the cylinder
block forms the second merging channel of the low pressure manifold.

6. The power generating apparatus of renewable energy type according to
claim 1, wherein the high pressure manifold of the hydraulic pump is
directly connected to the high pressure manifold of the hydraulic motor
through the high pressure oil line without any intervening valves that
restrict oil flow in the high pressure oil line, and wherein the low
pressure manifold of the hydraulic pump is directly connected to the low
pressure manifold of the hydraulic motor through the low pressure oil
line without any intervening valves that restrict oil flow in the low
pressure oil line.

7. The power generating apparatus of renewable energy type according to
claim 1, further comprising: a bypass passage which connects the high
pressure oil line and the low pressure oil line to bypass the hydraulic
motor; and a high pressure relief valve which is provided in the bypass
passage.

8. The power generating apparatus of renewable energy type according to
claim 1, further comprising: at least one accumulator valve; and at least
one accumulator which is connected to the high pressure oil line through
the at least one accumulator valve respectively, wherein the at least one
accumulator valve opens and closes to switch between a state where the at
least one accumulator is in fluid communication with the high pressure
oil line and a state where the at least one accumulator is isolated from
the high pressure oil line.

9. The power generating apparatus of renewable energy type according to
claim 1, wherein the high pressure valves of the hydraulic pump open to
allow hydraulic oil to flow from the working chambers of the hydraulic
pump to the high pressure oil line through the high pressure manifold
when pressure in the working chambers exceeds pressure in the high
pressure oil line.

10. The power generating apparatus of renewable energy type according to
claim 1, wherein the low pressure valves of the hydraulic pump open to
allow hydraulic oil to flow from the low pressure oil line to the working
chambers of the hydraulic pump through the low pressure manifold when
pressure in the working chambers falls below the pressure in the low
pressure oil line.

11. The power generating apparatus of renewable energy type according to
claim 1, wherein at least one of the high and low pressure valves of the
hydraulic pump and the hydraulic motor is a pressure-operated check valve
which is openable to allow hydraulic oil to flow in one direction due to
pressure difference across the at least one of the high and low pressure
valves.

12. The power generating apparatus of renewable energy type according to
claim 1, wherein the at least one of the high and low pressure valves of
the hydraulic pump and the hydraulic motor is an electronically
controlled valve, and wherein the power generating apparatus of renewable
energy type further comprises a controller which controls opening and
closing of the electronically controlled valve in phased relation to
cycles of movement of the piston to adjust net volume of hydraulic oil
displaced by the working chambers on each of the cycles.

13. The power generating apparatus of renewable energy type according to
claim 12, wherein the controller changes number of the working chambers
in idle state to adjust the net volume of the hydraulic oil displaced by
the working chambers on each of the cycles, the low pressure valves of
the working chambers in the idle state being kept open for a full cycle
of the movement of the piston.

14. The power generating apparatus of renewable energy type according to
claim 12, wherein the controller changes closure timing of at least one
group of the low pressure valves and the high pressure valves in each
cycle of the movement of the piston to adjust the net volume of the
hydraulic oil displaced by the working chambers on each of the cycles,
the closure timing being changed commonly for all valves belonging to the
at least one group of the low pressure valves and the high pressure
valves.

15. The power generating apparatus of renewable energy type according to
claim 1, wherein the at least one of the high and low pressure valves of
the hydraulic pump and the hydraulic motor is an electronically
controlled valve, the electronically controlled valve being a
face-sealing poppet valve which is not openable against a prescribed
pressure.

16. The power generating apparatus of renewable energy type according to
claim 1, wherein the at least one of the high and low pressure valves of
the hydraulic pump and the hydraulic motor is an electronically
controlled valve, and wherein the power generating apparatus of renewable
energy type further comprises a controller which controls opening and
closing of the electronically controlled valve to counter fluctuations in
torque and flow arising from asymmetric flow of hydraulic oil out of the
working chamber during each cycle of movement of the piston.

17. The power generating apparatus of renewable energy type according to
claim 1, wherein each of the low pressure valves of the hydraulic pump is
a normally open solenoid closed valve which opens passively when pressure
in the working chamber is less than pressure in the low pressure oil
line.

18. The power generating apparatus of renewable energy type according to
claim 1, further comprising: a pressure sensor which measures pressure of
hydraulic oil in the high pressure oil line, and a temperature sensor
which is provided in one of the high pressure oil line and the low
pressure oil line to measure temperature of hydraulic oil in the one of
the high pressure oil line and the low pressure oil line.

19. The power generating apparatus of renewable energy type according to
claim 1, wherein the power generating apparatus is a wind turbine
generator which generates power from wind as the renewable energy source.

Description:

TECHNICAL FIELD

[0001] This invention relates to a power generating apparatus of renewable
energy type which transmits rotation energy of a rotor obtained from a
renewable energy source to a power generating apparatus via a hydraulic
transmission having a combination of a hydraulic pump and a hydraulic
motor.

BACKGROUND ART

[0002] In recent years, from a perspective of preserving the environment,
it is becoming popular to use a power generating apparatus of renewable
energy type such as a wind turbine generator utilizing wind power and a
tidal current generator utilizing tidal current.

[0003] Such renewable energy devices traditionally employ a transmission
in the form of a gearbox to change the slow input speed of an energy
extraction mechanism such as the rotor of the wind or tidal turbine
generator to which kinetic energy of the renewable energy source is
inputted into a fast output speed to drive a power generating apparatus.
For example, in a common wind turbine generator, the rotation speed of
the rotor is approximately a few rotations to tens of rotations per
minute, whereas a rated speed of the power generating apparatus is
normally 1500 rpm or 1800 rpm and thus a mechanical gearbox. Thus, a
mechanical gearbox is provided between the rotor and the generator.
Specifically, the rotation speed of the rotor is increased to the rated
speed of the generator by the gearbox and then inputted to the generator.

[0004] Such transmission in the form of the gearbox is challenging to
design and build, as they are prone to failure and expensive to maintain
and replace or repair.

[0005] A further challenge in designing power generating apparatuses of
renewable energy type is extracting the optimum amount of energy by an
energy extraction mechanism in all conditions. The most effective devices
achieve this by holding the blades at a fixed pitch angle, and varying
the rotational speed of the blades proportionally to the wind or water
speed over the majority of the operating range, so as to maintain a more
or less constant `tip speed ratio`. Gearboxes at the scale required for
cost effective power generating apparatuses of renewable energy type are
invariably fixed ratio, so complex and failure-prone electronic power
conversion is required to provide electricity to an AC electricity
network.

[0006] In recent years, power generating apparatuses of renewable energy
type equipped with a hydraulic transmission adopting a combination of a
hydraulic pump and a hydraulic motor of variable displacement type are
getting more attention as an alternative to the mechanical gearboxes. In
such power generating apparatuses, it is possible to make the hydrostatic
transmission variable ratio even at large scales. Such a hydrostatic
transmission is also lighter and more robust than a gearbox, and lighter
than a direct generator drive unit. Thus, the overall cost of producing
electricity is reduced.

[0007] A structure of a hydraulic transmission applied to a wind turbine
generator is disclosed in Non-Patent Literature 1. The hydraulic
transmission includes a hydraulic pump connected to a rotor, a hydraulic
motor connected to a generator and a high pressure manifold and a low
pressure manifold arranged between the hydraulic pump and the hydraulic
motor respectively. Each of the hydraulic pump and motor includes a
plurality of cylinders and pistons and changes the displacement by
continuously activating and disabling of the working chambers formed
between the cylinders and pistons

[0008] As a related technique, Patent Literature 1 provides a wind turbine
generator using a hydraulic transmission having a combination of a
hydraulic pump driven by rotation of a rotor and a hydraulic motor
connected to a generator. In the hydraulic transmission of the wind
turbine generator, the hydraulic pump and the hydraulic motor are
connected via a high pressure reservoir and a low pressure reservoir
respectively. This allows the rotation energy of the rotor to be
transmitted to the generator via the hydraulic transmission. The
hydraulic pump is constituted of a plurality of pistons and cylinders and
a cam which moves the piston within the cylinder periodically.

[0009] Further, Patent Literature 2 describes a wind turbine generator
adopting a hydraulic transmission constituted of a hydraulic pump rotated
by a rotor, a hydraulic motor connected to a generator, and an oil path
arranged between the hydraulic pump and the hydraulic motor. In the
hydraulic transmission of this wind turbine generator, the hydraulic pump
is constituted of a plurality of sets of pistons and cylinders, cams
which periodically reciprocate the pistons in the cylinders, and high
pressure valves and low pressure valves which open and close with the
reciprocation of the pistons. By latching the piston near a top dead
center, a working chamber surrounded by the cylinder and the piston is
disabled, and then the displacement of the hydraulic pump is changed.

[0010] Although the hydraulic pump and the hydraulic motor are not
variable displacement type, Patent Literature 3 discloses a wind turbine
generator having a hydraulic pump and a hydraulic motor. The wind turbine
generator of Patent Literature 3 maintains the rotation speed of the
generator constant by adjusting the pressure of hydraulic oil to be
supplied from a hydraulic pump to a hydraulic motor. In this wind turbine
generator, a discharge side of the hydraulic pump is connected to an
intake side of the hydraulic motor via an inner space of the tower
functioning as a high pressure tank, and an intake side of the hydraulic
pump is connected to a discharge side of the hydraulic motor via a low
pressure tank arranged below the tower.

[0019] In the power generating apparatuses of renewable energy type such
as described above, it is desired to extract energy efficiently from the
renewable energy source and to maintain power generation efficiency high.
However, the renewable energy source used in such power generating
apparatuses are normally natural energy such as wind power and tidal
current and energy available for power generation fluctuates
significantly. Thus, it is difficult to perform energy extraction at
maximum efficiency. Particularly, the renewable energy is highly
temporally-unstable in a short period of time and it is necessary to
perform the control in response to the fluctuating energy in order to
extract energy efficiently.

[0020] In view of this, Non-Patent Literature and Patent Literatures 1 and
2, propose to adjust the displacement of the hydraulic pump or the
hydraulic motor in response to the fluctuating energy. However, none of
the literatures above suggests a specific structure for adjusting the
displacement of the hydraulic pump or motor with high accuracy according
to control signals. Further, as described in Patent Literature 3, in the
structure where a proportional valve is arranged the an oil line between
the high pressure tank and the hydraulic motor, it is difficult to
perform fine control as the proportional valve is located where the flow
rate of the hydraulic oil is great.

[0021] In view of the above issues, an object of the present invention is
to provide a power generating apparatus of renewable energy type which
can control the hydraulic transmission with high accuracy according to
control signals.

Solution to Problem

[0022] The present invention provides a power generating apparatus of
renewable energy type which generates power from a renewable energy
source. The power generating apparatus of renewable energy type may
include, but is not limited to: a rotating shaft driven by the renewable
energy source; a hydraulic pump driven by the rotating shaft; a hydraulic
motor which is driven by pressurized oil supplied from the hydraulic
pump; a generator coupled to the hydraulic motor; a high pressure oil
line through which a discharge side of the hydraulic pump is in fluid
communication with an intake side of the hydraulic motor; and a low
pressure oil line through which an intake side of the hydraulic pump is
in fluid communication with a discharge side of the hydraulic motor. And
each of the hydraulic pump and the hydraulic motor may include, but is
not limited to: a plurality of working chambers each of which is
surrounded by a cylinder and a piston reciprocating within the cylinder;
a high pressure manifold including first branch channels each connected
to the working chambers and a first merging channel connected to the high
pressure oil line, the first branch channels joining together and merging
into the first merging channel; a low pressure manifold including second
branch channels each connected to the working chambers and a second
merging channel connected to the low pressure oil line, the second branch
channels joining together and merging into the second merging channel; a
plurality of high pressure valves which are respectively provided in the
first branch channels of the high pressure manifold to open and close the
first branch channels; a plurality of low pressure valves which are
respectively provided in the second branch channels of the low pressure
manifold to open and close the second branch channels; and a casing which
accommodates the working chambers, the high pressure manifold, the low
pressure manifold, the high pressure valves and low pressure valves.

[0023] In the power generating apparatus of renewable energy type, the
high pressure valves are arranged in the first branch channels connected
to the working cylinders and the low pressure valves are arranged in the
second branch channels. Thus, it is possible to tweak the valves with
high accuracy in accordance with the control signals to the hydraulic
transmission. This achieves high power generation efficiency even in
fluctuations of the renewable energy.

[0024] Further, the casing accommodates the working chambers, the high
pressure manifold, the low pressure manifold, the high pressure valves
and, the low pressure valves, thereby downsizing the apparatus.

[0025] In the power generating apparatus of renewable energy type, at
least one of the hydraulic pump and the hydraulic motor may include a
cylinder block accommodated in the casing. The cylinders are provided
inside the cylinder block. And the first branch channels and the second
branch channels of the at least one of the hydraulic pump and the
hydraulic motor may be arranged inside the cylinder block.

[0026] In this manner, the first branch channels and the second branch
channels may be arranged inside the cylinder block. Thus, it is no longer
necessary to install a piping from the working chambers to the first and
second merging channels respectively, thereby downsizing the hydraulic
pump or the hydraulic motor.

[0027] In the power generating apparatus of renewable energy type, the
first merging channel of the high pressure manifold of at least one of
the hydraulic pump and the hydraulic motor may be provided inside an
endplate that forms an motor in a direction of a rotation central axis of
the at least one of the hydraulic pump and the hydraulic motor.

[0028] In this manner, the first merging channel of the high pressure
manifold of one of the hydraulic pump and the hydraulic motor is provided
inside the endplate that forms the end face of the casing. Thus, it is
possible to prevent the hydraulic oil having high pressure from leaking,
thereby improving liquid tightness.

[0029] In the power generating apparatus of renewable energy type, a
plurality of cylinder arrays may be arranged inside the cylinder block in
a circumferential direction of the at least one of the hydraulic pump and
the hydraulic motor, each of the cylinder arrays being constituted of the
cylinders aligned in a direction of a rotation central axis of the at
least one of the hydraulic pump and the hydraulic motor, a high pressure
communication channel may be provided inside the cylinder block between
adjacent two of the cylinder arrays, and the first branch channels
connected to the working chambers of the cylinders belonging to one or
the adjacent two of the cylinder arrays may be in fluid communication
with the first merging channel via the high pressure communication
channel.

[0030] In this manner, the first branch channels are in fluid
communication with the first merging channel via the high pressure
communication channel formed between adjacent two of the cylinder arrays.
Thus, it is possible to simplify the structure of the oil path, thereby
saving space.

[0031] In the power generating apparatus of renewable energy type, an
annular space between the casing and the cylinder block may form the
second merging channel of the low pressure manifold in the at least one
of the hydraulic pump and the hydraulic motor.

[0032] In this manner, the second merging channel of the low pressure
manifold is formed in the annular space between the casing and the
cylinder block. Thus, it is possible to utilize the space between the
casing and the cylinder block, thereby saving space and simplifying the
structure of the path.

[0033] In the power generating apparatus of renewable energy type, the
high pressure manifold of the hydraulic pump may be directly connected to
the high pressure manifold of the hydraulic motor through the high
pressure oil line without any intervening valves that restrict oil flow
in the high pressure oil line, and the low pressure manifold of the
hydraulic pump may be directly connected to the low pressure manifold of
the hydraulic motor through the low pressure oil line without any
intervening valves that restrict oil flow in the low pressure oil line.

[0034] When a valve is provided in the high pressure oil line, the valve
may restrict oil flow, thereby causing energy loss and resulting in
reduction of energy efficiency. Therefore, as described above, the high
pressure manifold of the hydraulic pump is directly connected to the high
pressure manifold of the hydraulic motor through the high pressure oil
line without any intervening valves, thereby producing power at high
efficiency without causing energy loss. Without any intervening valves in
the high pressure oil line and the low pressure oil line, it is possible
to simplify the piping structure connecting the hydraulic pump and the
hydraulic motor, thereby downsizing the apparatus.

[0035] In the power generating apparatus of renewable energy type may
further include a bypass passage which connects the high pressure oil
line and the low pressure oil line to bypass the hydraulic motor, and a
high pressure relief valve which is provided in the bypass passage.

[0036] For instance, the pressure in the high pressure oil line rises to a
setting pressure of the high pressure relief valve, the high pressure
relief valve opens to release the high pressure oil to the low pressure
oil line via the bypass passage, thereby keeping the pressure in the high
pressure oil line within an appropriate range.

[0037] The power generating apparatus of renewable energy type may further
include at least one accumulator valve and at least one accumulator which
is connected to the high pressure oil line through the at least one
accumulator valve respectively. The at least one accumulator valve may
open and close to switch between a state where the at least one
accumulator is in fluid communication with the high pressure oil line and
a state where the at least one accumulator is isolated from the high
pressure oil line.

[0038] In this manner, the accumulator valve opens and closes to connect
and disconnect the accumulator to the high pressure oil line. Thus, it is
possible to save surplus energy inputted to the hydraulic transmission
and to discharge the save surplus energy when the output power is short,
thereby achieving a stable power generation of the wind power energy,
which tends to fluctuate.

[0039] In the power generating apparatus of renewable energy type, the
high pressure valves of the hydraulic pump may open to allow hydraulic
oil to flow from the working chambers of the hydraulic pump to the high
pressure oil line through the high pressure manifold when pressure in the
working chambers exceeds pressure in the high pressure oil line.

[0040] Meanwhile, the low pressure valves of the hydraulic pump may open
to allow hydraulic oil to flow from the low pressure oil line to the
working chambers of the hydraulic pump through the low pressure manifold
when pressure in the working chambers falls below the pressure in the low
pressure oil line.

[0041] The above configurations may be selected as desired to eliminate
complicated valve control and simplify the control.

[0042] In the power generating apparatus of renewable energy type, at
least one of the high and low pressure valves of the hydraulic pump and
the hydraulic motor may be a pressure-operated check valve which is
openable to allow hydraulic oil to flow in one direction due to pressure
difference across the at least one of the high and low pressure valves.

[0043] In this manner, the check valve which opens and closes due to the
pressure difference is used for at least one of the high and low pressure
valves of the hydraulic pump and the hydraulic motor, thereby saving
electric power used to open and close the valve and also reducing running
cost. Further, the hydraulic oil is allowed to flow in one direction,
thereby preventing the hydraulic oil from regurgitating.

[0044] In the power generating apparatus of renewable energy type, the at
least one of the high and low pressure valves of the hydraulic pump and
the hydraulic motor may be an electronically controlled valve, and the
power generating apparatus of renewable energy type may also include a
controller which controls opening and closing of the electronically
controlled valve in phased relation to cycles of movement of the piston
to adjust net volume of hydraulic oil displaced by the working chambers
on each of the cycles.

[0045] In such case, the controller may change number of the working
chambers in idle state to adjust the net volume of the hydraulic oil
displaced by the working chambers on each of the cycles, the low pressure
valves of the working chambers in the idle state being kept open for a
full cycle of the movement of the piston.

[0046] In this manner, the number of the working chamber in idle state is
changed to adjust the net volume of the hydraulic oil displaced by the
working chambers, thereby controlling the displacement gradually and
making such control easier.

[0047] The controller may also change closure timing of at least one group
of the low pressure valves and the high pressure valves in each cycle of
the movement of the piston to adjust the net volume of the hydraulic oil
displaced by the working chambers on each of the cycles, the closure
timing being changed commonly for all valves belonging to the at least
one group of the low pressure valves and the high pressure valves.

[0048] In this manner, the closure timing of the valves of the same group
are synchronized, thereby improving the control stability and making it
easy to know the time for maintenance.

[0049] In the power generating apparatus of renewable energy type, the at
least one of the high and low pressure valves of the hydraulic pump and
the hydraulic motor may be an electronically controlled valve. The
electronically controlled valve is a face-sealing poppet valve which is
not openable against a prescribed pressure.

[0050] In such case, the at least one of the high and low pressure valves
of the hydraulic pump and the hydraulic motor may be an electronically
controlled valve, and the power generating apparatus of renewable energy
type may further include a controller which controls opening and closing
of the electronically controlled valve to counter fluctuations in torque
and flow arising from asymmetric flow of hydraulic oil out of the working
chamber during each cycle of movement of the piston.

[0051] In this manner, the fluctuations in torque and flow arising from
asymmetric flow is suppressed, thereby achieving a stable operation.

[0052] In the power generating apparatus of renewable energy type, each of
the low pressure valves of the hydraulic pump may be a normally open
solenoid closed valve which opens passively when pressure in the working
chamber is less than pressure in the low pressure oil line.

[0053] In this manner, each of the low pressure valves opens passively
when the pressure in the working chamber is less than the pressure in the
low pressure oil line, thereby saving electric power required for
exciting the valve. When the pressure in the working chamber increases
inappropriately, the low pressure valve is released, thereby preventing
abnormal pressure rise in the working chamber.

[0054] In the power generating apparatus of renewable energy type may
further include a pressure sensor which measures pressure of hydraulic
oil in the high pressure oil line, and a temperature sensor which is
provided in one of the high pressure oil line and the low pressure oil
line to measure temperature of hydraulic oil in the one of the high
pressure oil line and the low pressure oil line. For instance, the high
pressure valve or the low pressure valve may be controlled based on the
measured pressure and/or temperature, thereby achieving a proper control.

[0055] In the power generating apparatus of renewable energy type, the
power generating apparatus may be a wind turbine generator which
generates power from wind as the renewable energy source.

[0056] In the wind turbine generator, the wind power energy fluctuates
significantly. However, with the structure of the above power generating
apparatus of renewable energy type, the apparatus can be controlled with
accuracy in response to the fluctuations of the wind power energy,
thereby achieving stable power generation.

Advantageous Effects of Invention

[0057] According to the present invention, in the hydraulic pump and the
hydraulic motor, the high pressure valves are arranged in the first
branch channels connected to the working cylinders and the low pressure
valves are arranged in the second branch channels. Thus, it is possible
to tweak the valves with high accuracy in accordance with the control
signals to the hydraulic transmission. This achieves high power
generation efficiency even in fluctuations of the renewable energy.

[0058] Further, the casing of the hydraulic pump and the hydraulic motor
respectively accommodates the working chambers, the high pressure
manifold, the low pressure manifold, the high pressure valves and the low
pressure valves, thereby downsizing the apparatus.

BRIEF DESCRIPTION OF DRAWINGS

[0059] [FIG. 1]

[0060] FIG. 1 is a schematic view of an example structure of a wind
turbine generator.

[0061] [FIG. 2]

[0062] FIG. 2 is a schematic view of a hydraulic pump of the wind turbine
generator.

[0063] [FIG. 3]

[0064] FIG. 3 is a schematic view of a hydraulic motor of the wind turbine
generator.

[0065] [FIG. 4]

[0066] FIG. 4 is a sectional view illustrating a specific structure of the
hydraulic pump.

[0067] [FIG. 5]

[0068] FIG. 5 is a sectional view taken along the line A-A of FIG. 4.

[0069] [FIG. 6]

[0070] FIG. 6 is a sectional view taken along the line B-B of FIG. 5,
showing a cylinder block of the hydraulic pump.

[0071] [FIG. 7]

[0072] FIG. 7 is a plan view of the cylinder block taken from the
direction C of FIG. 4.

[0073] [FIG. 8]

[0074] FIG. 8 is a sectional view taken along the line D-D of FIG. 4,
showing an endplate of the hydraulic pump.

[0075] [FIG. 9]

[0076] FIG. 9 is a sectional view showing a specific structure of the
hydraulic motor.

[0077] [FIG. 10]

[0078] FIG. 10 is a sectional view taken along the line E-E of FIG. 9.

[0079] [FIG. 11]

[0080] FIG. 11 is a sectional view of the endplate of the hydraulic motor,
taken along the line F-F of FIG. 9.

[0081] [FIG. 12]

[0082] FIG. 12 is a perspective external view of the hydraulic motor.

[0083] [FIG. 13]

[0084] FIG. 13 is a sectional view showing a modified example of the
hydraulic motor.

DESCRIPTION OF EMBODIMENTS

[0085] A preferred embodiment of the present invention will now be
described in detail with reference to the accompanying drawings. It is
intended, however, that unless particularly specified, dimensions,
materials, shape, its relative positions and the like shall be
interpreted as illustrative only and not limitative of the scope of the
present invention.

[0086] A general structure of the wind turbine generator in relation to
the present invention is explained hereinafter. FIG. 1 is a schematic
view showing an example structure of the wind turbine generator. FIG. 2
is a schematic view showing an example structure of the hydraulic pump of
the wind turbine generator. FIG. 3 is a schematic view showing an example
configuration of the hydraulic motor of the wind turbine generator.

[0087] As an example of the wind turbine generator, a three-bladed wind
turbine generator is used. However, the present invention is not limited
to this example and can be applied to various types of wind turbine
generators.

[0088] As illustrated in FIG. 1, a wind turbine generator 100 includes a
rotor 10 rotated by the wind, a hydraulic transmission 11 for increasing
rotation speed of the rotor 10, a generator 12 for generating electric
power, a nacelle 14 and a tower 15 for supporting the nacelle 14.

[0089] The rotor 10 is configured such that a rotating shaft 18
(equivalent of a rotation shaft of the hydraulic pump) is connected to a
hub 17 having blades 16. Specifically, three blades 16 extend radially
from the hub 17 and each of the blades 16 is mounted on the hub 17
connected to the rotating shaft 18. By this, the power of the wind acting
on the blades 16 rotates the rotor 10 as a whole, and the rotation of the
rotor 10 is inputted to the hydraulic transmission 11 via the rotating
shaft 18. The huh 17 may house a pitch driving mechanism for changing a
pitch angle of the blades 16.

[0090] The hydraulic transmission 11 includes a hydraulic pump 20 of a
variable displacement type which is rotated by the rotating shaft 18, a
hydraulic motor 21 of a variable displacement type which is connected to
the generator 20 via a crank shaft 31, and a high pressure oil line 22
and a low pressure oil line 23 which are arranged between the hydraulic
pump 20 and the hydraulic motor 21. The high pressure oil line 22
connects a discharge side of the hydraulic pump 20 and an intake side of
the hydraulic motor 21. The low pressure oil line 23 connects a discharge
side of the hydraulic motor 21 and an intake side of the hydraulic pump
20. By this, the rotation of the rotating shaft 18 rotates the hydraulic
pump 20, thereby creating a pressure difference between the high pressure
oil line 22 and the low pressure oil line 23. The pressure difference
drives the hydraulic motor 21. The hydraulic transmission 11 adjusts a
speed increasing ratio (displacement ratio of the hydraulic pump 20 and
the hydraulic motor 21) in accordance with the rotation speed of the
rotating shaft 18 so as to maintain the rotation speed of the hydraulic
motor 21 at a constant speed. The hydraulic transmission is described in
details later.

[0091] The generator 12 is connected to the hydraulic motor 21 of the
hydraulic transmission 11. The known synchronous generator or induction
generator can be used as the generator 12. The torque having the rotation
speed that is almost constant is inputted from the hydraulic motor 21 to
the generator 12 and then the generator 12 produces AC power having a
frequency that is almost constant.

[0092] The nacelle 14 supports the hub 17 of the rotor 10 rotatably and
houses a variety of devices such as the hydraulic transmission 11 and the
generator 12. The nacelle 14 is further supported on the tower 15
rotatably and may be turned in accordance with the wind direction by a
yaw motor which is not shown.

[0093] Further, a rotation speed meter 40 which measures the rotation
speed of the rotating shaft 18, a first pressure meter 41 which measures
the pressure in the high pressure oil line 22, and a temperature sensor
39 which measures a temperature of the hydraulic oil in the high pressure
oil line 22 are provided in the wind turbine generator 100. The
measurement results of the rotation speed meter 40 and the first pressure
meter 41 are sent to a controller 1 to control the hydraulic pump 20 and
the hydraulic motor 21.

The controller 1 controls each component of the wind turbine generator. A
variety of signals are inputted to the controller 1, such as a rotation
speed signal of the rotation speed meter, a high pressure oil signal of
the first pressure meter 41, a hydraulic oil temperature signal of the
temperature sensor 39, a pressure signal of an accumulator which is
described later, a rotation speed signal of the hydraulic pump 20 and a
rotation speed signal of the hydraulic motor 21. Based on at least one of
the input signals as described above, high pressure valves 65, 85, low
pressure valve 66, 86, accumulator valves 31, 32, the high pressure
relief valve 37, and the low pressure relief valve 47 may be controlled.
The controller 1 includes a variety of control devices and the controller
1 and such control devices may be located in different locations either
inside or outside of the nacelle 14, so that the controller 1 may form a
distributed control system. It is also possible that the functions of
more than one of the controllers 1 and the control devices may be
combined into one computer processing unit.

[0094] The accumulator 33, 34 is connected to the high pressure oil line
22 via accumulator valve 31, 32. The accumulator 31, 32 may be, for
instance, a bladder type or a piston type in which air and hydraulic
fluid are separated by a deformable bag. In the accumulator 33, 34, the
hydraulic oil of high pressure is introduced during an accumulating
process so as to deform the bladder or push the piston to compress the
air. In contrast, during a pressure-releasing process, the compressed air
expands or the high pressure air from outside pushes the bladder or the
piston to push the hydraulic oil out of the accumulator 33,34.

[0095] A second pressure meter (not shown) is provided between the
accumulator valve 31, 32 and the accumulator 33, 34. The second pressure
meter measures the pressure of the hydraulic oil in the accumulator 33,
34.

[0096] Measurement results of the first pressure sensor 41 and the second
pressure sensor are sent to controller 1 to be used for controlling the
opening and closing of the accumulator valve 31, 32. The controller 1
preferably controls the opening and closing of the accumulator valve 31,
32 based on the measurement results of the first pressure sensor 41 and
the second pressure sensor. In this manner, the opening and closing of
the accumulator valve 31, 32 is controlled to bring the accumulator 33,
34 in or out of communication with the high pressure oil line 22. Thus,
it is possible to save surplus energy inputted to the hydraulic
transmission 11 and to discharge the surplus energy when the output power
is short, thereby achieving a stable power generation of the wind power
energy, which tends to fluctuate.

[0097] The bypass passage 36 is provided between the high pressure oil
line 22 and the low pressure oil line 23. And, a high pressure relief
valve 37 is provided in the bypass passage 70 to maintain the pressure of
the hydraulic oil in the high pressure oil line 22 not greater than the
setting pressure. In this manner, when the pressure in the high pressure
oil line 22 rises to the setting pressure of the high pressure relief
valve 37, the high pressure relief valve 37 automatically opens so as to
release the high pressure oil to the low pressure oil line 23 via the
bypass passage 36.

[0098] Further, the hydraulic transmission 11 has an oil tank 42, a
supplementary line 43, a boost pump 44, an oil filter 45, a return line
46 and a low pressure relief valve 47.

[0099] All or part of the return flow from the hydraulic motor 22 may pass
through at least one of these units.

[0100] As shown in FIG. 2, the hydraulic pump 20 has a plurality working
chambers 53 surrounded by the cylinders 51 and the pistons 52, the cam 58
having a cam surface which engages with the pistons 52, the high pressure
manifold 60 connecting each of the working chambers 53 and the high
pressure oil line 22, the low pressure manifold 62 connecting each of the
working chambers and the low pressure oil line 23, and sets of a high
pressure valve 65 and a low pressure valve 66, each set of which is
provided for each of the working chambers 53.

[0101] The cylinder 51 is a cylindrical space formed in a cylinder block
that is described later. Inside the cylinder 51, is formed the working
chamber 53 surrounded by the cylinder 51 and the piston 52.

[0102] From the perspective of operating the pistons 52 smoothly along the
cam surface of the cam 58, each of the pistons 52 preferably includes a
piston body 52A which moves slidingly in the cylinder 51 and a piston
roller or a piston shoe which is mounted on the piston body 52A and
engages with the cam surface of the cam 58. The "piston roller" is a
member that comes in contact with the cam surface of the cam 58 and rolls
thereon. The "piston shoe" is a member that comes in contact with the cam
surface of the cam 58 and slides thereon.

[0103] The example illustrated in FIG. 2 shows the pistons 52 each of
which has the piston body 52A and the piston roller 52B.

[0104] The cam 58 is installed on an outer circumference of the rotating
shaft 18 via a cam mount 59. For one rotation of the rotating shaft 18,
the cam 58 moves each of the pistons 52 of the hydraulic pump 20 upward
and downward many times, thereby increasing the torque of the hydraulic
pump 20. From this point of view, the cam 58 is preferably a ring cam
that has a cam surface defining a plurality of waves with concave
portions 58A and convex portions 58B that are alternately disposed around
the rotating shaft 18.

[0105] The cam 58 is fixed to the cam mount 59 by means of a securing
member 57 such as a bolt, a key and a pin.

[0106] The high pressure manifold 60 includes the first branch channels
60A each connected to the working chambers 53 and the first merging
channel 60B connected to the high pressure oil line 22. The first branch
channels 60A join together and merge into the first merging channel 60B.

[0107] The low pressure manifold 62 includes the second branch channels
62A each connected to the working chambers 53 and the second merging
channel 62B connected to the low pressure oil line 23. The second branch
channels 62A join together and merge into the second merging channel 62B.

[0108] The high pressure valve 65 is arranged in the first branch channels
60A of the high pressure manifold 60, whereas the low pressure valve 66
is arranged in the first branch channels 62A of the low pressure manifold
62. By opening and closing the high pressure valve 65 and the low
pressure valve 66, it is possible to change a communication status
between the high pressure oil line 22 and each of the working chambers 53
and between the low pressure oil line 23 and each of the working chambers
53. The opening and closing of the high pressure valve 65 and the low
pressure valve 66 is performed in synchronization with the upward and
downward motion of the piston 52.

[0109] Preferably, the high pressures valve 65 open to allow hydraulic oil
to flow from the working chambers 53 of the hydraulic pump 20 to the high
pressure oil line 22 through the high pressure manifold 60 when pressure
in the working chambers 53 exceeds pressure in the high pressure oil line
22. The low pressure valves 66 preferably open to allow hydraulic oil to
flow from the low pressure oil line 23 to the working chambers 53 of the
hydraulic pump 20 through the low pressure manifold 62 when pressure in
the working chambers 53 falls below the pressure in the low pressure oil
line 23. By this, it is possible to eliminate complicated valve control
and simplify the control.

[0110] Further, the low pressure valves 66 of the hydraulic pump is
preferably a normally open solenoid closed valve which opens passively
when pressure in the working chamber 53 is less than pressure in the low
pressure oil line 23. In this manner, each of the low pressure valves 66
opens passively when the pressure in the working chamber is less than the
pressure in the low pressure oil line 23, thereby saving electric power
required for exciting the valve. When the pressure in the working chamber
53 increases inappropriately, the low pressure valve 66 is released,
thereby preventing abnormal pressure rise in the working chamber 53.

[0111] In the hydraulic pump 20, when the cam 58 rotates with the rotating
shaft 18, the piston body 52A of each piston 52 moves upward and downward
periodically. In the hydraulic pump 20, a pump step in which the piston
52 moves from the bottom dead center to the top dead center and an intake
step in which the piston 52 moves from the top dead center to the bottom
dead center are performed repeatedly. In the pump step, the high pressure
valve 65 is opened and the low pressure valve 66 is closed so as to feed
the high pressure oil in the working chamber 53 through the first branch
channel 60A and the first merging channel 60B to the high pressure oil
line 22 in this order. Meanwhile, in the intake step, the high pressure
valve 65 is closed and the low pressure valve 66 is opened so as to
supply the low pressure oil from the low pressure oil line 23 through the
second merging channel 62B and the second branch channels 62A to the
working chamber 53 in this order.

[0112] In this manner, the hydraulic pump 20 is rotated by the rotation of
the rotating shaft 18, thereby generating the pressure difference between
the high pressure oil line 22 and the low pressure oil line 23.

[0113] As illustrated in FIG. 3, the hydraulic motor 21 includes a
plurality of hydraulic chambers 73 formed between the cylinders 71 and
the pistons 72, the cam 78 having a cam surface which engages with the
pistons 72, the high pressure manifold 80 connecting each of the working
chambers 73 and the high pressure oil line 22, the low pressure manifold
82 connecting each of the working chambers 73 and the low pressure oil
line 23, and the high pressure valve 85 and the low pressure valve 86
that are provided for each of the working chambers 73.

[0114] The cylinder 71 is a cylindrical space provided for a cylinder
block that is described later. Inside the cylinder 71, formed is the
working chamber 73 surrounded by the cylinder 71 and the piston 72.

[0115] From the perspective of converting the upward and downward motion
of the pistons 72 smoothly to the rotary motion of the cam 78, each of
the pistons 72 preferably includes a piston body 72A which moves
slidingly in the cylinder 71 and a piston roller or a piston shoe 72C
which is mounted on the piston body 72A and engages with the cam surface
of the cam 78. Herein, the "piston roller" is a member that comes in
contact with the cam surface of the cam 78 and rotates thereon. The
"piston shoe" is a member that comes in contact with the cam surface of
the cam 78 and slides thereon.

[0116] The cam 78 is an eccentric cam that is disposed eccentrically with
respect to a shaft center O of a crank shaft 13 connected to the
generator 12. While the pistons 72 complete one set of upward and
downward motions, the cam 78 and the crank shaft 13 on which the cam 78
is mounted, complete one rotation.

[0117] The high pressure manifold 80 includes first branch channels 80A
each connected to the working chambers 73 and a first merging channel 80B
connected to the high pressure oil line 22. The first branch channels 80A
join together and merge into the first merging channel 80B.

[0118] The low pressure manifold 82 includes second branch channels 82A
each connected to the working chambers 73 and the second merging channel
82B connected to the low pressure oil line 23. The second branch channels
82A join together and merge into the second merging channel 82B.

[0119] The high pressure valve 85 is arranged in the first branch chancel
80A of the high pressure manifold 80, whereas the low pressure valve 86
is arranged in the first branch channel 82A of the low pressure manifold
82. By opening and closing the high pressure valve 85 and the low
pressure valve 86, it is possible to change a communication status
between the high pressure oil line 22 and each of the working chambers 73
and between the low pressure oil line 23 and each of the working chambers
73. The opening and closing of the high pressure valve 85 and the low
pressure valve 86 is performed in synchronization with the upward and
downward motion of the piston 72.

[0120] In the hydraulic motor 21, the pistons 72 are moved up and down by
utilizing the pressure difference between the high pressure oil line 22
and the low pressure oil line 23. In the hydraulic motor 21, a motor step
in which the pistons 72 move from the top dead center to the bottom dead
center and a discharge step in which the pistons 72 move from the bottom
dead center to the top dead center are performed repeatedly. In the motor
step, the high pressure valve 85 is opened and the low pressure valve 86
is closed so as to supply the hydraulic oil having high pressure (high
pressure oil) from the high pressure oil line 22 through the first
merging channel 80B and the first branch channel 80A of the high pressure
manifold 80 to the working chamber 73 in this order. Meanwhile, in the
discharge step, the high pressure valve 85 is closed and the low pressure
valve 86 is opened so as to discharge hydraulic oil in the working
chamber 73 through the first branch channel 82A and the first merging
channel 82B of the low pressure manifold 82 to the low pressure oil line
23 in this order.

In this manner, the high pressure oil fed into the working chamber 73 in
the motor step pushes down the piston 72 to the bottom dead center, and
then the crank shaft 13 rotates with the cam 78.

[0121] In the hydraulic transmission described above, at least one of the
high pressure valve 65, 85 and the low pressure valve 66, 86 of the
hydraulic pump 20 and the hydraulic motor 21 may be a pressure-operated
check valve which is openable to allow hydraulic oil to flow in one
direction due to pressure difference across the at least one of the high
pressure valve 65, 85 and the low pressure valve 66, 86. In this manner,
the check valve which opens and closes due to the pressure difference is
used for at least one of the high pressure valve 65, 85 and the low
pressure valve 66, 86 of the hydraulic pump 20 and the hydraulic motor
21, thereby saving electric power used to open and close the valve and
also reducing running cost. Further, the hydraulic oil is allowed to flow
in one direction, thereby preventing the hydraulic oil from
regurgitating.

[0122] Further, the at least one of the high pressure valve 65, 85 and the
low pressure valve 66, 86 of the hydraulic pump 20 and the hydraulic
motor 21 may be an electronically controlled valve, and the controller 1
may control opening and closing of the electronically controlled valve in
phased relation to cycles of movement of the piston to adjust net volume
of hydraulic oil displaced by the working chambers 53, 73 on each of the
cycles. In such case, the controller 1 may change number of the working
chambers 53, 73 in idle state to adjust the net volume of the hydraulic
oil displaced by the working chambers 53, 73 on each of the cycles, the
low pressure valves 66, 86 of the working chambers 53, 73 in the idle
state being kept open for a full cycle of the movement of the piston. In
this manner, the number of the working chambers 53, 73 in idle state is
changed to adjust the net volume of the hydraulic oil displaced by the
working chambers 53, 73, thereby controlling the displacement gradually
and making such control easier.

[0123] The controller 1 may also change closure timing of at least one
group of the low pressure valves 66, 86 and the high pressure valves 65,
86 in each cycle of the movement of the piston to adjust the net volume
of the hydraulic oil displaced by the working chambers 53, 73 on each of
the cycles, the closure timing being changed commonly for all valves
belonging to the at least one group of the low pressure valves 66, 86 and
the high pressure valves 65, 86. In this manner, the closure timing of
the valves of the same group are synchronized, thereby improving the
control stability and making it easy to know the time for maintenance.

[0124] Further, the at least one of the low pressure valves 66, 86 and the
high pressure valves 65, 86 of the hydraulic pump 20 and the hydraulic
motor 21 may be an electronically controlled valve. The electronically
controlled valve is a face-sealing poppet valve which is not openable
against a prescribed pressure.

[0125] Furthermore, the at least one of the low pressure valves 66, 86 and
the high pressure valves 65, 86 of the hydraulic pump 20 and the
hydraulic motor 21 may be an electronically controlled valve, and the
controller 1 may control opening and closing of the electronically
controlled valve to counter fluctuations in torque and flow arising from
asymmetric flow of hydraulic oil out of the working chamber 53, 73 during
each cycle of movement of the piston. In this manner, the fluctuations in
torque and flow arising from asymmetric flow is suppressed, thereby
achieving a stable operation.

[0126] The specific structure of the hydraulic transmission 11 of the wind
turbine generator in relation to the present invention is now explained.

(Hydraulic Pump Structure)

[0127] The structure of the hydraulic pump is illustrated in FIG. 4 to
FIG. 8. FIG. 4 is a sectional view illustrating a specific structure of
the hydraulic pump. FIG. 5 is a sectional view taken along the line A-A
of FIG. 4. FIG. 6 is a sectional view taken along the line B-B of FIG. 5,
showing a cylinder block of the hydraulic pump. FIG. 7 is a plan view of
the cylinder block taken from the direction C of FIG. 4. FIG. 8 is a
sectional view taken along the line D-D of FIG. 4, showing an endplate of
the hydraulic pump.

[0128] As shown in FIG. 4 and FIG. 5, the hydraulic pump 20 is mounted on
the rotating shaft 18. Specifically, the cam mount 59 is fixed to the
outer circumference of the rotating shaft 18 and the cam 58 is mounted on
the cam mount 59. Further, in the example illustrated in FIG. 4, the
hydraulic pump 20 is arranged between rotating shaft bearings 19A and 19B
for supporting the rotating shaft 18 rotatably on the nacelle side.

[0129] On the outer circumference of the cam mount 59, a pump casing 50 is
fixed via a pump bearing 55. The pump casing 50 covers each part of the
cylinders 51, the pistons 52, the high pressure manifold 60, the low
pressure manifold 62, the high pressure valve 65 (see FIG. 6), the low
pressure valve 66 and the cams 58, and also prevents the hydraulic oil
from leaking to outside. The pump casing 50 includes a pair of end plates
50A and 50B arranged in the axial direction of the rotating shaft 18 and
a cylindrical case 50C arranged between the pair of end plates 50A and
50B.

[0130] The hydraulic pump 20 may include a plurality of the modules, each
of the modules being composed of a cylinder block 54 having at least one
cylinder 51, the piston 52, the high pressure manifold 60, the low
pressure manifold 62, the high pressure valve 65 and the low pressure
valve 66 that are provided for each of the cylinders 51 of the cylinder
block 54. The module is formed by the cylinder block 54 and attached
components such as the piston 52, the high pressure valve 65 and the low
pressure valve 66.

[0131] As shown in FIG. 6, each of the cylinder blocks 54 is an arc-shaped
member in cross-section that extends in a direction of the rotation
central axis or a circumferential direction of the rotating shaft 18.

[0132] When the cylinder block 54 extends in the direction of the rotation
central axis of the rotating shaft 18, each of the cylinder blocks 54
includes at least one cylinder array 56. Each of the cylinder blocks 54
is composed of the cylinders 51-1, 51-2, 51-3 and 51-4, arranged in the
axial direction of the rotating shaft 18. In the cylinder block 54, a
pair of the pistons 52, the high pressure valve 65 and the low pressure
valve 66 (see FIG. 6) are arranged for each of the cylinders 51.

[0133] As illustrated in FIG. 5, the hydraulic pump 20 includes a
plurality of modules arranged in a circumferential direction of the
rotating shaft 18, each of the modules being composed of the cylinder
block 54 of the arc shape, the piston 52, the high pressure valve 65 and
the low pressure valve 66 that are provided for each of the cylinders 51
of the cylinder block 54.

[0134] In the cylinder block 54, a plurality of the cylinder arrays 56 are
arranged in the circumferential direction of the rotating shaft 18.
Inside the cylinder block 54, a plurality of the first branch channels
60A are formed in the circumferential direction of the central rotation
axis from each of the cylinders 51. A high pressure communication channel
60C is also provided inside the cylinder block between a pair of adjacent
cylinder arrays in the direction of the rotation axis as shown in FIG. 7.
The first branch channels 60A arranged in the same array are connected to
the high pressure communication channel 60C via the high pressure valve
65. In such case, the first branch channels 60A may be connected to the
working chambers 53 of the cylinders 51 belonging to the adjacent two of
the cylinder arrays 56.

[0135] The high pressure communication channel 60C extends to the endplate
50B and as shown in FIG. 8, connected to the first merging channel 60B
formed in the endplate 50B. The high pressure communication channel 60C
has openings that are formed in the circumferential direction of the
rotation central axis in the endplate 50B. The openings are in fluid
communication with the first merging channel 60B. The first merging
channel 60B is formed into a ring shape along the circumferential
direction of the rotation central axis and connected to at least one of
high pressure oil line 22. The first merging channel is formed into a
circular ring shape in the drawing. However, this is not limitative and
the first merging channel 60B may be formed into any shape such as a
rectangular-ring shape.

[0136] In this manner, the first merging channel 60B of the high pressure
manifold 60 is provided inside the endplate 50B that forms the end face
of the pump casing 50. Thus, it is possible to prevent the hydraulic oil
having high pressure from leaking, thereby improving liquid tightness.

[0137] Further, the first branch channels 60B are in fluid communication
with the first merging channels 60A via the high pressure communication
channel 60C formed between adjacent two of the cylinder arrays. Thus, it
is possible to simplify the structure of the oil path, thereby saving
space.

[0138] In the preferred embodiment, the first branch channels 60B are in
fluid communication with the first merging channels 60A via the high
pressure communication channel 60C. However, this is not limitative, the
first branch channels 60B may be directly connected to the first merging
channels 60A. In the preferred embodiment, a plurality of cylinder blocks
54 having an arc-shaped cross-section are arranged in the circumferential
direction of the rotation central axis. However, this is not limitative
and the cylinder blocks having a ring-shaped cross-section may be
arranged in the circumferential direction.

[0139] With the above structure, the high pressure oil pushed out of the
working chamber 53 is introduced through the first branch channel 60A and
then the first merging channel 60B o the high pressure oil line 22
connected to the endplate 50B.

[0140] As shown in FIG. 4 to FIG. 6, the low pressure manifold 62 is
arranged on an outer side of the cylinder block 54 in a radial direction
of the rotating shaft 18 and on an inner side of the pump casing 50. The
low pressure manifold 62 includes the second branch channel 62 extending
on the outer side of the working chamber 53 in the radial direction of
the rotating shaft 18, and the second merging channel 62B formed between
the outer periphery of the cylinder block 54 and the pump casing 50.

[0141] The low pressure valve 66 is arranged in the second branch channel
62A. The second merging channel 62B is provided for the plurality of the
cylinders 51 and in fluid communication with the low pressure oil line 23
connected to an upper part of the hydraulic pump 20. In this manner, the
low pressure oil of the low pressure oil 23 is supplied through the
second merging channel 62B and the second branch channel 62A in this
order to each of the working chambers 53 via the low pressure valve 66.

[0142] As described above, the first branch channel 60A and the second
branch channel 62A are formed inside of the cylinder block 54. Thus, it
is no longer necessary to install a piping from the working chambers 53
to the first and second merging channels 60B, 62B respectively, thereby
downsizing the hydraulic pump 20.

[0143] Further, the second merging channel 62B of the low pressure
manifold 62 is formed in the annular space between the pump casing 50 and
the cylinder block 54. Thus, it is possible to utilize the space between
the pump casing 50 and the cylinder block 54, thereby saving space and
simplifying the structure of the path.

(Hydraulic Motor Structure)

[0144] The structure of the hydraulic motor is illustrated in FIG. 9 to
FIG. 12. FIG. 9 is a sectional view showing a specific structure of the
hydraulic motor. FIG. 10 is a sectional view taken along the line E-E of
FIG. 9. FIG. 11 is a sectional view of the endplate of the hydraulic
motor, taken along the line F-F of FIG. 9. FIG. 12 is a perspective
external view of the hydraulic motor.

[0145] As shown in FIG. 9 and FIG. 10, the cam 78 of the hydraulic motor
21 is an eccentric cam that is disposed eccentrically with respect to a
shaft center O of a crank shaft 13 connected to the generator 12 via
shaft connection part 75.

[0146] A motor casing 70 is fixed via cam bearings 76A, 76B to the shaft
connection part 75 and a cam end 77 and the shaft connecting part 77
respectively connected to each end of the cam 78. The motor casing 70
covers each part of the cylinders 71, the pistons 72, the high pressure
manifold 80, the low pressure manifold 82, the high pressure valve 85,
the low pressure valve 86 and the cams 78, and also prevents the
hydraulic oil from leaking to outside. The motor casing 70 includes a
pair of end plates 70A and 70B arranged in the axial direction of the
crankshaft 13 and a cylindrical case 70C arranged between the pair of end
plates 70A and 70B (see FIG. 12).

[0147] In the hydraulic motor 21, provided is the cylinder block 74 formed
around the cam 78. The cylinder block 74 includes at least one cylinder
71, and a pair of the piston 72, the high pressure valve 85 and the low
pressure valve 86 are provided for each of the at least one cylinder 71.
Further, the example illustrated in FIG. 10, the piston 72 includes a
piston body 72A which moves slidingly in the cylinder 71, and a piston
shoe 72C that is mounted on the piston body 72A and is in engagement with
the cam surface of the cam 78.

[0148] The hydraulic motor 21 may include a plurality of the modules
arranged in a circumferential direction of the crankshaft 13. Each of the
modules may be composed of the cylinder block 74 partially covering the
cam surface of the cam 78, the piston 72 provide for each cylinder 71 of
the cylinder block 74, the high pressure valve 85 and the low pressure
valve 86 that are provided for each of the at least one cylinder 71 of
the cylinder block 74.

[0149] The module may be composed of the cylinder block 74 disposed
circumferentially around a center axis O of the crankshaft 13 in a
continuous manner and the component group attached thereto such as the
piston 72, the high pressure valve 85 and the low pressure valve 86.

[0150] Each of the cylinder blocks 74 is a member extending in the
direction of the rotation central axis or the circumferential direction
of the cam 78.

[0151] When the cylinder block 74 extends in the direction of the rotation
central axis, each of the cylinder blocks 74 includes at least one
cylinder array which includes a plurality of cylinders 71 arranged in the
axial direction of the cam 78. In the cylinder block 74, a pair of the
pistons 72, the high pressure valve 85 and the low pressure valve 86 are
arranged for each of the cylinders 71.

[0152] The hydraulic motor 21 includes a plurality of modules arranged in
a circumferential direction of the cam 78, each of the modules being
composed of the cylinder block 74 of the arc shape, the piston 72, the
high pressure valve 85 and the low pressure valve 86 that are provided
for each of the cylinders 71 of the cylinder block 74.

[0153] In the cylinder block 74, a plurality of the cylinder arrays are
arranged in the circumferential direction of the cam 78. Inside the
cylinder block 74, a plurality of the first branch channels 80A are
formed in the circumferential direction of the central rotation axis from
each of the cylinders 71. The high pressure communication channel 80C is
also provided inside the cylinder block 74 between a pair of adjacent
cylinder arrays in the direction of the rotation axis, in the manner
similar to the structure of the hydraulic pump 20 of FIG. 7. The first
branch channels 80A arranged in the same array are connected to the high
pressure communication channel 80C via the high pressure valve 85. In
such case, the first branch channels 80A may be connected to the working
chambers 73 of the cylinders 71 belonging to the adjacent two of the
cylinder arrays.

[0154] The high pressure communication channel 80C extends to the endplate
70B and as shown in FIG. 11, connected to the first merging channel 80B
formed in the endplate 70B. The high pressure communication channel 80C
has openings that are formed in the circumferential direction of the
rotation central axis in the endplate 70B. The openings are in fluid
communication with the first merging channel 80B. The first merging
channel 80B is formed into a ring shape along the circumferential
direction of the rotation central axis and connected to at least one of
high pressure oil line 22. The first merging channel is formed into a
rectangular-ring shape in the drawing. However, this is not limitative
and the first merging channel 80B may be formed into any shape such as a
circular-ring shape.

[0155] In this manner, the first merging channel 80B of the high pressure
manifold 80 is provided inside the endplate 70B that forms the end face
of the pump casing 70. Thus, it is possible to prevent the hydraulic oil
having high pressure from leaking, thereby improving liquid tightness.

[0156] Further, the first branch channels 80B are in fluid communication
with the first merging channels 80A via the high pressure communication
channel 80C formed between adjacent two of the cylinder arrays. Thus, it
is possible to simplify the structure of the oil path, thereby saving
space.

[0157] In the preferred embodiment, the first branch channels 80B are in
fluid communication with the first merging channels 80A via the high
pressure communication channel 80C. However, this is not limitative, the
first branch channels 80B may be directly connected to the first merging
channels 80A.

[0158] As described above, the hydraulic transmission comprises the
hydraulic pump 12, the hydraulic motor 14, the high pressure oil line 16
and the low pressure oil line 18. The discharge side of the hydraulic
pump 12 is connected to the intake side of the hydraulic motor 14 and the
intake side of the hydraulic pump 12 is connected to the discharge side
of the hydraulic motor 14.

[0159] In the drawings, the hydraulic transmission 11 is illustrated with
only one hydraulic motor 21. However, the hydraulic transmission 11 may
include more than one hydraulic motor 21 and the hydraulic motors 21 may
be connected to the hydraulic pump 21 via the high pressure oil lines 22
and the low pressure oil lines 23 respectively.

[0160] With the above structure, the high pressure oil supplied from the
hydraulic pump 20, is introduced from the high pressure oil line 22
connected to the end plate 70B of the hydraulic motor 21 through the
first merging channel 80B and then the first branch channel 80A of the
high pressure manifold 80 to the working chamber 73.

[0161] The low pressure manifold 82 is arranged on an outer side of the
cylinder block 74 in a radial direction of the cam 78 and on an inner
side of the motor casing 70. The low pressure manifold 82 includes the
second branch channel 82 extending on the outer side of the working
chamber 73 in the radial direction of the cam 78, and the second merging
channel 82B formed between the outer periphery of the cylinder block 74
and the motor casing 70.

[0162] The low pressure valve 76 is arranged in the second branch channel
82A. The second merging channel 82B is provided for the plurality of the
cylinders 71 and in fluid communication with the low pressure oil line 23
connected to an upper part of the hydraulic motor 21. In this manner, the
low pressure oil discharge from the working chamber 73 is supplied via
the low pressure valve 86 through the second branch channel 82A and then
the second merging channel 82B of the low pressure manifold 82 to each of
the working chambers 73.

[0163] As described above, the first branch channel 80A and the second
branch channel 82A are formed inside of the cylinder block 74. Thus, it
is no longer necessary to install a piping from the working chambers 73
to the first and second merging channels 80B, 82B respectively, thereby
downsizing the hydraulic motor 21.

[0164] Further, the second merging channel 82B of the low pressure
manifold 82 is formed in the annular space between the motor casing 70
and the cylinder block 74. Thus, it is possible to utilize the space
between the motor casing 70 and the cylinder block 74, thereby saving
space and simplifying the structure of the path.

[0165] FIG. 13 shows a modified example of the above hydraulic motor. The
same reference numerals are given for those components that are the same
as the hydraulic motor as described above.

[0166] FIG. 13 shows a hydraulic motor 21' of a double motor type. The
hydraulic motor 21' includes two motor units 21A and 21B that are
connected via an end plate 70B'. Each of the motor units 21A and 21B
includes the cylinder 71, the piston 72, the high pressure manifold 80,
the low pressure manifold 82, the high pressure valve 85 (see FIG. 10),
and the low pressure valve 86. The motor units 21A and 21B are housed in
a casing 70'. The casing 70' includes the end plate 70A'-1, 70A'-2 that
are provided on both end in the central axis direction of the hydraulic
motor 21', an end plate 70B' provided between the end plates 70A'-1,
70A'-2, and a cylindrical case 70'C-1 or 70'C-2 provided between the end
plate 70A'-1 or 70A'-2 and the end plate 70B'. The motor units 21A and
21B has a cam 78' which penetrates through the end plate 70B'. The first
merging channel 80B of the high pressure manifold 80 may be provided in
the end plate 70B' and the first merging channel 80 may be configured to
be used by both of the motor units 21A and 21B, thereby simplifying the
piping structure.

[0167] As described above, in the preferred embodiments, the high pressure
valves 65, 85 are arranged in the first branch channels 60A, 80A
connected to the working cylinders 53, 73 and the low pressure valves 66,
86 are arranged in the second branch channels 62A, 82A. Thus, it is
possible to tweak the valves with high accuracy in accordance with the
control signals to the hydraulic transmission 11. This achieves high
power generation efficiency even in fluctuations of the renewable energy.

[0168] Further, the pump casing 50 and the motor casing 70 of the
hydraulic pump 20 in FIG. 4 to FIG. 8 and the hydraulic motor 21 in FIG.
9 to FIG. 12 accommodate the working chambers 53, 73, the high pressure
manifolds 60, 80, the low pressure manifolds 62, 82, the high pressure
valves 65, 85 and the low pressure valves 66, 86, thereby downsizing the
apparatus.

[0169] In particular, the high pressure manifold 60 of the hydraulic pump
20 is directly connected to the high pressure manifold 80 of the
hydraulic motor 21 through the high pressure oil line 22 without any
intervening valves, thereby producing power at high efficiency without
causing energy loss.

[0170] While the present invention has been described with reference to
exemplary embodiments, it is obvious to those skilled in the art that
various changes may be made without departing from the scope of the
invention.

[0171] For instance, the preferred embodiment uses the exemplary case to
which the present invention is applied. But the present invention is also
applicable to the tidal current generator. The tidal current generator
herein indicates a power generating apparatus which is installed in
places such as the ocean, river and lake and uses energy of the tidal
current to produce electric power. The basic structure of the tidal
current generator is the same as that of the wind turbine generator 100
except for that the rotor 10 is rotated by the tidal current instead of
the wind. The same reference numbers are used here to explain the
components that are common to the wind turbine generator 100. The tidal
current generator includes the rotor 10 which is rotated upon receiving
the tidal current, the hydraulic transmission 11 which increases the
rotation speed of the rotor 10 and the generator 12 which produces
electric power.

[0172] As described above, the hydraulic transmission 11 of the tidal
current generator is configured such that the high pressure valves 65, 85
are arranged in the first branch channels 60A, 80A connected to the
working cylinders 53, 73 and the low pressure valves 66, 86 are arranged
in the second branch channels 62A, 82A. Thus, it is possible to tweak the
valves with high accuracy in accordance with the control signals to the
hydraulic transmission 11. This achieves high power generation efficiency
even in fluctuations of the renewable energy.

[0173] Further, the pump casing 50 and the motor casing 70 of the
hydraulic pump 20 and the hydraulic motor 21 accommodate the working
chambers 53, 73, the high pressure manifolds 60, 80, the low pressure
manifolds 62, 82, the high pressure valves 65, 85 and the low pressure
valves 66, 86, thereby downsizing the apparatus.

REFERENCE SIGNS LIST

[0174] 1 Controller

[0175] 10 Rotor

[0176] 11 Hydraulic transmission

[0177] 12 Generator

[0178] 13 Crankshaft

[0179] 18 Rotating shaft

[0180] 20 Hydraulic pump

[0181] 21 Hydraulic motor

[0182] 22 High pressure oil line

[0183] 23 Low pressure oil line

[0184] 31, 32 Accumulator valve

[0185] 33, 34 Accumulator

[0186] 36 Bypass passage

[0187] 37 High pressure relief valve

[0188] 38 Second pressure meter

[0189] 40 Rotation speed meter

[0190] 41 First pressure meter

[0191] 50 Pump casing

[0192] 50A, 50B, 70A, 70B End plate

[0193] 50C, 70C Cylindrical case

[0194] 51, 71 Cylinder

[0195] 52, 72 Piston

[0196] 53, 73 Working chamber

[0197] 58, 78 Cam

[0198] 60, 80 High pressure manifold

[0199] 60A, 80A First branch channel

[0200] 60B, 80B First merging channel

[0201] 62A, 82A Second branch channel

[0202] 62B, 82B Second merging channel

[0203] 65, 85 High pressure valve

[0204] 66, 86 Low pressure valve

Patent applications by Alasdair Robertson, Midlothian GB

Patent applications by Atsushi Maekawa, Tokyo JP

Patent applications by Daniil Dumnov, Midlothian GB

Patent applications by Hauke Karstens, London GB

Patent applications by Kazuhisa Tsutsumi, Tokyo JP

Patent applications by Masayuki Shimizu, Tokyo JP

Patent applications by Robert Fox, Midlothian GB

Patent applications by Stephen Laird, Midlothian GB

Patent applications by Stephen Salter, Midlothian GB

Patent applications by Toshihide Noguchi, Tokyo JP

Patent applications by Uwe Stein, Midlothian GB

Patent applications by William Rampen, Midlothian GB

Patent applications by Yasuhiro Korematsu, Tokyo JP

Patent applications by MITSUBISHI HEAVY INDUSTRIES, LTD.

Patent applications in class With control means for structure storing work driving energy (e.g., accumulator, etc.)

Patent applications in all subclasses With control means for structure storing work driving energy (e.g., accumulator, etc.)